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Entry M0274    1.2.3.3    pyruvate oxidase

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Step 07

Phosphate initiates a nucleophilic attack on the kinetically stable anion radical adduct.

GIF of Reaction Step M0274.stg07


Comment: Phosphate attacks the kinetically stable anion radical adduct. Kinetics experiments have shown the presence of phosphate to enhance the rate of electron transfer [4]. The negative charge resulting from the nucleophilic attack by phosphate is thought to reduce the potential of the intermediate and therefore increase the driving force of the following electron transfer to FAD.
An alternative mechanism has been proposed in [4] which involves the homolytic fragmentation of a phosphate radical adduct.



Mechanisms

Bimolecular Nucleophilic Addition

Mechanism Components

Bond Formation
Bond Order Change

Amino acids involved in the reaction step.

Amino Acid Location of Function Activity Function
Glu59B Side Chain spectator Hydrogen Bond Acceptor
Val394A Side Chain spectator Radical Stabiliser
Ile480A Side Chain spectator Radical Stabiliser
Phe121A Side Chain spectator Radical Stabiliser
Phe479A Side Chain spectator Radical Stabiliser
Gln122A Side Chain spectator Hydrogen Bond Donor

Organic Cofactors involved in the reaction step

Cofactor Type Cofactor Activity Function
FAD FAD612A spectator Not Active
Thiamine diphosphate TPP611A reactant Covalently Attached
Activator
Electrostatic Stabiliser
Hydrogen Bond Donor

Metal Cofactors involved in Step 07

Metal Type Metal Identity Chain Activity Function
magnesium MG 610 A spectator Substrate Binding

Reactive Centre

Bonds Formed Bonds Cleaved Bonds Changed in Order Atom Types Involved
C-O
None
The C-C bond changes from a double to single bond
C
O

View similar reactions in MACiE.


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